"Today the Palestinians close the black chapter of division between them," Israel Radio quoted Palestinian Authority President Mahmoud Abbas as saying at the ceremony.
The ceremony was delayed an hour by disputes on seating arrangements and a decision Abbas would be the only speaker. Hamas politburo head Khaled Mashaal also was prevented from sitting next to Abbas, the report said.
Egyptian Foreign Minister Nabil al-Arabi and Egyptian Intelligence chief Murad Muwafi flanked Abbas on the stage. Members of 13 Palestinian factions and Egyptian officials attended the ceremony.
The actual agreement was inked Tuesday in Cairo.
Ghazi Hamed deputy foreign minister in Gaza told Israel Radio Israel's occupation of Palestinian land remains the root of all problems. The unity agreement will improve Hamas' position and unify Palestinians in Gaza and the West Bank, he said.
Hamas expects Israel to withdraw to the 1967 borders and allow the return of all Palestinian refugees to their homes in Israel, he said.
Senior Palestinian official Nabil Shaath told Israel Radio the agreement does not require Hamas to recognize Israel because by signing the agreement Hamas has agreed to halt attacks, he said.